There is known a valve drive device capable of independently setting a phase of one intake valve and a phase of another intake valve of plural intake valves mounted for a combustion chamber. In this regard, for example, Patent document 1 discloses a valve drive device for varying valve timings of first and second engine valves, which are the same type and which are mounted for a combustion chamber.
Also, for example, Patent Documents 2 and 3 disclose techniques which might be relevant to the present invention in an aspect of control. In an engine control apparatus disclosed in Patent Document 2, a cam phase difference is reduced by a variable phase cam control mechanism and a throttle opening degree of a throttle valve is reduced when it is determined that engine brake is needed in a vehicle state. In a control apparatus of an internal combustion engine disclosed in Patent Document 3, a closing timing of an intake valve is more retarded and an throttle opening degree is more reduced as a brake pedal operation amount is larger so as to make an intake air amount constant, when a vehicle is decelerated by operating the brake pedal.
In addition, in constitution, Patent Document 4 discloses a spark ignition internal combustion engine, as a technique relevant to the present invention, provided with: a variable compression ratio mechanism capable of varying a mechanical compression ratio; and a variable valve timing mechanism capable of independently controlling an opening timing and a closing timing of the intake valve.